1. Field of the Invention
The present invention relates to a thermal transfer recording apparatus for image recording on a recording medium by transfer of ink from an ink sheet, and a facsimile apparatus utilizing such a recording apparatus.
2. Related Background Art
In general thermal transfer printers utilize an ink sheet consisting of a substrate film coated with heat-fusible (or heat sublimable) ink, and effect image recording by selectively heating said ink sheet with a thermal head according to an image signal, thereby transferring thus fused (or sublimed) ink onto a recording sheet. Since the ink sheet is generally a so-called one-time ink sheet in which the ink is completely transferred to the recording sheet by a single image recording, it is necessary, after the image recording of a character or a line, to advance the ink sheet by a distance corresponding to the recorded length, thereby securely bringing an unused portion of the ink sheet to the next recording position. Consequently the amount of the ink sheet used increases, and such thermal transfer printers tend to have high running costs in comparison with ordinary thermal printers utilizing thermosensitive recording paper.
In order to prevent this drawback, there have already been proposed thermal transfer printers in which the recording sheet and the ink sheet are transported with different speeds, as disclosed in Japanese Patent Appln. Laid-Open Nos. 57-83471 and No. 58-201686 and in the Japanese Patent Publication No. 62-58917.
Also used in such thermal transfer printers, there is already known a multi-print ink sheet capable of plural (n) image recordings. In continuous image recording of a length L, such an ink sheet allows a reduction in the length thereof, transported during or after image recording, to a value smaller than L (said value being L/n; n&gt;1). The efficiency of use of the ink sheet can therefore be increased to n times the conventional efficiency, and a reduction in the running cost of the thermal transfer printer can be expected. Such a recording method will hereinafter be called the multi printing method.
In such a multi printing, the ink constituting the ink layer of the ink sheet is heated n times, and ink transfer to the recording sheet is achieved by generating a shearing force between an ink layer portion fused in each heating and an unfused ink layer portion. In such a printing method, if the recording of a line does not take place immediately after the recording of a preceding line, the temperature of the ink layer is lowered, and the shearing strength between the fused ink layer portion transferred to the recording sheet and the unfused ink layer portion increases so that it becomes more difficult to separate the ink sheet from the recording sheet. This phenomenon becomes more conspicuous when the recording data of a line contains a large number of black data.